Waveguide switch device



April 1s, 1961 Filed DeG. 29. 1958 R. M. WALKER ET AL 2,980,873

WAVEGUIDE SWITCH DEVICE 4 Sheets-Sheet 1 [FIGA April 18, 1961 R. M.WALKER ET AL 2,980,873

WAVEGUIDE SWITCH DEVICE 4 Sheets-Sheet 2 Filed Dec. 29, 1958 @Em KWF-E IODR O AKS-I 4 TWRS ,v All 4 6 N .EMI 4 m 5 EMBBM 6 M VDDAJ. 1 7 M GWMDDHRT A 0 6 .I N 1 f 7 r www@ 5 Mmmm .fn Q .m 0 Y l B I 3 4. M zulilum v UMH. 2 4 h 2 a 2J 2 2 M 51 \V\\ n 8 4 w1 U K w 4 ATT'Ys.

F\ 1 1 IIF April 18, 1961 R. M. WALKER ET AL 2,980,873

WAVEGUIDE SWITCH DEVICE 4 Sheets-Shea?I 5 Filed Dec. 29, 1958 INVENTORS.RICHARD M. WALKER BERNARD D. BERKOWITZ,

ARTHUR A. BLAISDELL 0nd VINCENT J. MSTRETTA BYMQIVOICu/)MAM *Wl AT TYs.

April 18, 1961 R. M. WALKER ETAL 2,980,873

WAVEGUIDE SWITCH DEVICE 4 Sheets-Sheet 4 Filed DeG. 29, 1958 SECTIONCLOSED 68 68 69@ @E [FIG] 24 lFIG. I9

INVENTORS. RICHARD M. WALKER,

ATTYS..

WAVEGUIDE SWITCH DEVICE Richard M. Walker, Boston, Bernard D. Berkowitz,

Waltham, Arthur A. Blaisdell, Natick, and Vincent J.

Mistretta, Framingham, Mass., assignors `to Microwave Associates, Inc.,Burlington, Mass., a corporation f Massachusetts Vllliled Dec. 29, 1958,Ser. No. 783,520 Claims. (Cl. S33- 98) The tield tof this invention isthat of waveguide attenuators and relates, more particularly, towaveguide switches or shutters for opening and closing a waveguidepassage with regard to the transmission of microwave energy.

A typical, although by no means the only use of waveguide switches, inthat instance commonly referred to as shutters, is in radar duplexersystems employing transmitreceive (TR) or anti-transmit-receive'(ATR)tubes. During normal operation of all systems of this type which employgas discharge TR tubes, the highly sensitive pointcontact crystaldetector of the system is protected by the so-calledkeepalive in the TRtube which continuously supplies electrons in a small resonant gapwhich, due to these electrons, will fire and electrically shunt thewave'-A Y guide at comparatively low power levels which cannot damagethe crystal detector therebehind. Howeven' whenV the installation isVinoperative, with its power turned olf, the keep alive is inoperativeand the gap will fire only? at a power level of much highermagnitude'than when the system is operative. In this case the TR tube,beingyuntired, will pass power at levels suiiiciently high to damageVthe sensitive detector. Such power may come, for example, from thetransmitter of a nearby operating radar set feeding into the antenna ofthe inoperative set to be protected.

It has been proposed to provide additional protection for the crystaldetectors of such systems by mechanically shorting the waveguidetransmission line when power is atentf 4 turned off, Veither by way ofvanes inserted across the waveguide or by providing the resonant gapswith structures for mechanically bridging them. Such provisions are notsatisfactory from the point of view of reliability because they requirelarge linear motion of the shorting structure and because they relay onmetallic contacts for their electric performance. Linear motion isobjectionable in any equipment which must withstand shock and vibration,and because it requires relatively large operating forces. Furthermore,devices which depend for their operation on linear motion of onecomponent relative to the remainder of the device will undergo changesin operating characteristics when subjected to acceleration at variousangles to the direction of the linear motion. VMetallic contacts areobjectionable for similar reasons and because they are subject to wearwhich destroys the electrical characteristics of the device, and becausethe contact surfaces will acquire deformations causing the device Vtostick in open or closed position.

.Objects of this invention are to provide a waveguide shutter whichessentially eliminates the above defects by minimizing the forcerequired to operate the device and the possibility of wear, to providesuch a device which due to its very small motion permits fast operationand also minimizes force, impact and wear, to provide such a devicewhich eliminates the use of metallic contacts for establishing itselectrical function, and to provide a waveguide shutter whosecharacteristics are not appreciably affected by acceleration in anydirection, such as, for example, might be caused by shock and vibration.

Other objects are to provide waveguide shutters, which when in closedposition, will eifect substantially complete reflection of microwaveenergy and will allow only negligible lealrage of the microwave energythrough the waveguide, and which, when in open position, will permittransmission of microwave energy through the switch with minimuminsertion loss,.to provide a shutter whose characteristics are notadversely affected by shock or vibration; which is fast-acting, notsubject to excessive wear,V

and which requires a minimum of power for its actuation, and to providea shutter system which is simple, compact, fully `reliable and efcient,and which can be easily adapted forinsertion in various types ofwaveguide transmission lines.

A brief summary of the nature and substance of theinvention and of someof its main aspects is as follows:

`Systems according to the invention comprise, for attachment within awaveguide section of a transmission line: a vane, means forrotatablymounting the vane In theherein described preferred embodiment of-thisinvention the actuating means are electromagnetic and, in a specific,particularly practical aspect, comprise, a permanent magnet rotatablewith the shutter, and an electromagnet disposed adjacent to the walls ofthe waveguide section such as to align the shutter magnet with the fieldof the electromagnet when the electromagnet is energized, causing theshutter to rotate between closed and open positions, a permanent biasingforce such as spring means being utilized for returning the shutter tonormal position when the electromagnetic eld is withdrawnf In thepreferred embodiment of this invention, the-shutter `comprises a thinvane of a configuration similar to but slightly smaller then thecross-section of the waveguide passage and has axial pivots integraltherewith for rotatably mounting the shutter in low friction bearingsdisposed in the center of opposite waveguide walls. In alternativeembodiments, the vane is provided with one or more irises resonant withthe capacitive or inductive gaps existing between the vane and thewaveguide when the switch is in closed position, these gaps providingmechanical clearance for rotation of the vane' within the waveguidesection passage, thereby increasing the microwave attenuation elected bythe switch. In other alternative embodiments, the vane edges areprovided with dielectrically-lled slots to provide a filter section inthe gaps between'the vane and the waveguide when the switch is in closedposition; these lter sections also increase the microwave attenuationeffected by the switch. y

In another aspect of the invention, lumped impedances are provided nearopposite vane edges in'the form of metallic bodies or buttons adjacentthe pivots of the vane at the guide walls, these buttons constitutingmatching reactances for eliminating the reactive mismatch resulting fromthe vane in open position. 'Y

These and other objects, aspects of novelty, and details of constructionwill appear from the following description of a practical embodimentwith several modifications thereof. A

The description of theseyembodiments refers to drawings in which n Fig.1 is an exploded isometric view of the waveguide switch according tothisV invention;

Fig. 2 is a side view of awaveguide shutter according` Fig. 5 is asection on line 5 5 of Fig. 3;

Y "agesozs t j Figs. 6, 10, 14 and 18` are partial views of alternativeembodiments of the shutter vane according to the invention shown as theywould appear in closed position` lookinginto-a waveguide; l Figs. 7',11, 15 and 19` are sections on the correspondingly numberedlines' ofFigs. 6, 10, 14 and 1'8;

Figs. 8, 12, l6`andr 20 are partial views of the shutter i of Figs. 6,1'0, 14 and l8trespectively, shown as theyy would appear in openpositionlooking into a waveguide; and' Figs.' 9`, 13,Y 17 anclJ 21 areequivalent electric circuitl The shutter'is connected in thetransmission line in conventional manner, here by the liange connectors,4 and 6, as shown. The arrow w indicates the direction of flow ofmicrowave energy through the waveguide. v y

The shutter assembly includes a rectangular waveguide section 7comprising the broad webs 8 Vand 9, which correspond to the broad wallsof the waveguide sections 2` and 3, and the narrow webs, 11 and 12,which correspond to the narrow walls of the waveguide sections 2 and 3.The waveguide section 7 is constructed of the usual waveguide'materialsuch as brass or aluminum.

The web 11 yhas a central aperture 14 to receive' the bearing 16,preferably a ball bearing as shown, a' shoulder 17 being provided forproperly positioning the bearing. The web 12 has a similar aperture 18and shoulder 19 for receiving and positioning the bearing 21.'

The shutter proper 22, as shownin Figs. 1 and 3, is formed by a thin,rectangular, metallic vane 23 of slightly smaller dimensions than thewaveguide passage 13. Cylindrical buttons, 24 and 26 are coaxiallymounted on the vane on its longitudinal vaxis and have axially threadedbores 30. An axial pivot screw 27 is locked in threaded engagement withthe button 24, and a second axial pivot screw 28 is similarlyk locked inthreaded engagement with the button 26. Sleeves 29 and 31 areY fittedover the screws 27 and 28 respectively, for properly positioning thevane 23 between the bearings 16 and 21, equally spaced from 4thewaveguide webs 11 and 12.

The second pivot screw holds a permanent magnetV 32, in fixed relationto the shutter vane 23, by the screw head 33, for rotation as a unit.The magnet has a flattened side 34 and is positioned on the screw 28 sothat its pole axis as indicated in Fig. 2,-normally extends parallel tothe. direction of flow of microwave energy through the shutter; assemblyand transversely of the broad faces of the vane 23. A stop intheV formof a pin 36 projecting above `the bearing 16, is so positioned anddimensioned that. rotational movement of the magnet 32 is confined witha 90 arc. The spiral spring 37 engages the web 12 and the axial pivotscrew 27y for biasing the vane 23 to the position shown in Fig. 3whereby the magnet 32 will abut the stop 36 as shown in Fig. 2. The vane23 will then be disposed within the passage 13 transversely ofthedirection of ow of the microwave energy therethrough. It will be evidentthat the magnet can be rotated away from the stop 36 until the oppositeend of the magnet face 34 abuts the stop and that such motioncorresponds to a 90 rotation of the vane 23 moving it to a positionwithin the passage 13 parallel to the flow of microwave energyytherethrough. The plate 37.1 and the screw 37.2 serve to hold thebearing 21 in place'A and the screw 37.2 at the. same timeanchorsoneend' of the spring 37. The other end of 'the spring.' isstaked to theY spring collar 37.3, which in turn is heldY against thesleeve 29 by the head of the pivot screw 27.

At either end ,ofY the waveguide passage 1'3 the webs 8, 9, 11, and 12,.which define the passage .13, meet in laterally extending flanges 38 and39 which form a rectilinearly peripheral groove 41 as shownV in Figs. 2,3, 4 and 5. The core piece 42, notched as at 43 to fit over the web 12and grooved as Yat 44 to provide clearance for the-spring 37, is fixedwithin the rectilinear groove 41 adjacent. the web` 12. SeriesVconnected field coils 46.1v and: 46.2"'wound on cylindrical` coreVpieces 47: are

., mounted within the rectilinear groove 41, one` adjacent each ofv thewebs 81 and 9respectively, and are fixed to the corepie'ce42v by thescrews 48; 'I'hercoreA pieces 49 and 51, notched as at 52 and 53,respectively,to fitl the web 11, are mounted within the rectilineargroove 41 adjacent the web 111` to provide the gap 54 therebetween, andarejoined' each toV alcore piece 47 by a screw 56. Bores` 57 extendingthrough the waveguide anges 38 and 39 and through the. core'. pieces 42,49 and 51, are provided for fastening the waveguide switchy 1 within awaveguide transmission line.

In this manner an electromagnet is provided for establishingl a magneticcircuit comprising the core pieces,

42', 47, 49 and 51, directed across the gap 54, and capable of rotatingthe permanent magnet 32 therein to the extentV permitted by the stop 36.

yA. non-magnetic cover 59, held to core pieces 49 and S1 by-the screws61 and having a sealing gasket 62, closes the gap 54. The coils, 46.1and 46.2 are confined in potting compound 63 which lillsthe groove 41adjacent Y the webs 8 and 9, the nuts 70 being encased in said potf tingof coil' 46.1 kto'receive the screws 66. Terminals 64 for theleads 65.from the coils 46.2 as shown in Fig.

Y3,V are fastened to the switch device by the screws 66.

The nuts- 70 are electrically connected internally to the ends of thewindings of 46.1. For 4the sake of simplicity this is not illustrated inthe drawings. The core piece 42 is provided with an external groove 67for receiving and protecting the leads 65.

. The operation of devices according to the invention as exemplifiedbythe above-described embodiment is as follows.

It will be readily understood that a waveguide switch according to thisinvention, within a waveguide transmission line as shown in Fig. 2,V forexample within the transmission line to the receiver crystal inconventional radar equipment, will have its vane 22 normally biased intothe position transversely of the waveguide passage 13 by the spring '37as shown in Figs. 3 and 4 and will therefore reflect substantially allmicrowave energy directed towards it within the waveguide section 2.Thus the shutter `will protect the receiver crystal of the radar set,while it isin power-off condition, from injurious exposure to randomhigh-power R.F. signals such as might be emitted by other radarequipment operating in the vicinity.

r When/the radar set incorporating the shutter is placed in operativecondition with the TRv tube keep alive on, thek shutter is renderedineffective by connecting the terminals l64. to a D.C. source withVsuitable switching apparatus. The coils. 46l will thus be excited andwill establish a magneticv field across the gap 54 which will rotate themagnet 32 into alignment therewith against the bias of the spring 37 tothe extent permitted by the stop 36, thereby rotating the shutter 22 toa position parallel to the wave-guide passage 13. In this position, theshutter will permitv normal operation vof the radar set. TheAfollowing'favorable mechanical conditions will prevail at closed andopen kpositions and during movement from one to the other.

` The` shutter according to the invention has a very short and positivemotion and is therefore fast-acting, and it will not be subject toinjury or disalignment when exposed to shockl or vibration; It willialsobe noted that its operation inball bearings minimizes the possibility ofVwear and the force required foroperation.` Furthermore-the shutteroperation?v is `not dependent upon' the making and breaking of metallicelectrical contacts within the switch, thevane being always spaced fromthe waveguide walls. This feature also eliminates-possibilities ofwearand furaesdsvs 4 will retain its operating characteristics even when theswitch device isaccelerated in any direction.` u nlike shutter deviceswhich are not so balanced, this 'dev1ce 1sV particularly useful Ain high-speed aircraft and missiles.

Withregard tofelectrical operating conditions, the leakageinlclosed'position and the insertion loss inopen positionare ofprimaryimportance; these conditions are optimally favorablerin devicesconstructed according tothe present4 invention forthe following reasons.i i i When in closed position as shownin Figs. 3 and 4, the shuttervanepresents a short circuit across thewaveguide, reflecting essentiallyall the power. As indicated above, this `is the `normal position of ashutter used for the protection of crystal detectors in inoperativeradar systems. In anidealconstructiom the leakage of the closed shuttershould be zero. Theleakage in structures such as shown in Figs. 3 and 4is determined by the capacitance between the vane edges and the broadwaveguide walls. This capacitance can'be made larger with a resultingdecrease in leakage by making the gap indicated at g of Fig. 3 smaller,or by increasing the vane thickness indicated at ft of Fig. 4. Thepossible increase in capacitance `is controlled by` practicalmanufacturing conditions and assembly tolerances. In previous practice,lleakage has been controlledfby metallic contacts and has been dependentupon cleaness, wear and humidity. In the present invention, negligibleleakage is permitted but this leakage does not vary with age or changein environmental conditions. The leakage value is less than 1% in powerover the entire yfrequency range of the waveguide system in which theshutterv is installed.` Lower leakage values may be obtained over 4anarrower frequency range with shutter embodiments to be described below.

In open position, the vane is essentially -reectionless and thereforethe R.F. signalI passes freely through the shutter device to thereceiver, without appreciable insertion loss. This favorable operationis materially aided by the provision of the abovedescribed buttons 24and 26 for the following reason. In open position, the vane divides vane23. `This iris is selected to be resonant -at a frequency considerablyhigher than'operating frequency. vIn this case, the equivalent circuit,as shown in Fig. 9, includes iris inductance`69a and iris capacitance69b as well as the gap capacitance 68a resulting from the gap requiredfor mechanical clearance between the Vclosed vane 68 and the broadwaveguide web 8. The iris represents an inductive parallelcircuit landat operating frequency this inductanceis series Yresonant with the fgapcapacitance 68a thereby presentinga complete short circuitV across thewaveguide. This type of`vane` effects substantially completeattenuation, tests indicating leakage of less than 0.1% of the incidentpower over a 12% frequency range. in the open position, vane 68 causesinsertion losses similar to those measured for the simple vane 23according to Fig. 3.

` The vane 71 as shown in Figs. 10 to l2 is provided with slots 72.1,72.2 lled with dielectric material 73. Each/ slot represents a shortchoke section to provideva Ifilter in'each gap as shown by theequivalent circuit Fig. 13 wherein 72a are the gap impedances betweenthe vane impedance 71 and the broad waveguide walls 8 and-9. Theeffective depth of the slots determines whether these impedances yaireinductive or capacitive and this effective depth and hence the type ofimpedance can be controlled by varying the dielectric constant of thematerial which yfills the slots. Tests indicate that a slot of a depthapproximately equal to 1A; of a guide wavelength has an inductive effectand that a slot of a depth approximately equal to 3/3 of a guidewavelength has a capacitive effect; in either case, the electricalcharacteristics of this vane `over Va 12% frequency range are similar tothat of the vane 68 according to Figs. 6 to 9.

The vane 74 shown in Figs. 14 to 16 has a single slot 76 filled with adielectric material 77. Tests indicate that in this instance a slotdepth slightly less than 1A! of a guide Wavelength has a capacitiveelect and increases the attenuating effect of the closed vane over a'12% frequency range to approximately that of the vane 68 of Figs. 6 to8. Fig. 17 shows the reduced capacitances 76a existing in the gapbetween the vane Y74v and the broad waveguide the waveguide into twoequal guides each nearly half the full waveguide cross section.k Theopen vane inevitably introduces a certain amount of capacitive andresistive .mismatch The capacitive reactance is largely matched .entlybe shown below by actual'performance data. The

major contribution to the insertion loss of components of this type isreflected power which can be determined by VSWR measurements. Thematching buttons' are very effective in providing a very low VSWR over awide frequency range, indicatingpractically zero insertion loss. One ofthe first models constructed according to the presentinvention,lwith-buttons 24, 26 according to Figs. 3, 4-and 5, had thenegligible insertion loss Aof less than 0.1 dbover a 12%A frequencyrange. The VSWRv over the 12% frequency range was less than 1.06.

The above-described construction with the vane normally closedtransversely across the waveguide, assumes a normally tie-energizedcontrolling magnetic motor. This manner of operation can be reversed .byrotating the magnetic armature 32 on its shaft 28 to put it parallel tothe vane. The shutter is then normally open'with` the motor de-energiiedwhich,"when energized, will rotate the vane in opposite direction intoclosed position.

The alternative embodiments according to Figs. 6 to 2l illustrate vaneconstructions which can be used with shutters such as shown in Fig. 3,these alternative embodiments effecting even greater attenuation ofmicrowave en ergy when the switch is in closed position,'as comparedtothe simple vane of Fig. 3.

`Thevane 68 shown in Figs. 6 to 8 s provided with a Yrectangular iris 69but is otherwise the same as the shutter webs `8 and 9. i

The vane 78 shown in Figs.` 18 to 20 is provided with diaphragms '79 and81 forming the inductive irises 82 and 83. 'Il-lese inductances 82u and83a are adjusted to resonate with the capacitances 78a and 79a and` 81aas indicated in Fig. 2l, existing in the gaps between the vane 78 andthe diaphragms 79V and 81 respectively, and the broad waveguide webs.The vane 78 as provided withthe diaphragms 79 and 81 has an atenuatingeffect approximately equal to that of the vane 68 of Figs. 6 to 8.

From the above practical test results it will be evident that devicesaccording to the invention provide substantially complete microwaveattenuation when in closed position and Vpermit substantially completemicrowave transmission when in open position. It will also be evidentthat this device is suitable for use with Vvarious types of Awaveguideapparatus, such as for example the so-called short-slot hybrid or thefolded magic tee, to perform functions such as that of an attenuator orof a rotary switch from one antenna to another', or of a variable powerdivider.

It .will be further evident that certain features of the invention-suchas the central suspension of the vane, the clearance between vane andguide section, and the mismatch eliminating buttons between vane andguide wall positions-did not necessarily have to be used withrectangular guides but have more general application.

It should be understood that `the present disclosure is for the purposeof ilustration only and that this invention includes all modificationsand equivalents which fall within the scope of the appended claims.

We claim:

i l. Waveguide switch apparatus comprising: a straight rectangularwaveguide section of substantially uniform internal cross section-fthrougheutits length; a substane tially flat rectangular metallicshutter lvane having a thicknesjs'which is -a-minor fractionof anyinternalcross-V sectional .dimension of saidwaveguide section, said vanebeing dimensioned in the length and-width directions perpendicular toits thickness dimension evectively to ll theinternal transverse crosssection of said waveguide without touching any of the walls thereof;means for mounting the shutter v ane for rotation within said `guidesection, about an axis of symmetry of the guide section and the vane, toeachoftwo fixed positions, one of which is a closed positiontransversely of the guide sectionand the other of which is Van openposition parallel to the guide section axis; and metallic bodies ofsubstantially cylindrical cross section permanently aixed to each nartrow side edge of said vane concentric with the rotational axis thereof,each of said bodies presenting a substantially circular surface adjacentand spaced from the confronting narrow wall portions, respectively, ofthe waveguide section, said bodies being dimensioned and located toconstitute axially symmetrical lumped inductance elements for matchingthe capacitive reactance across the Waveguide section introduced by thevane in the open position.

2. Waveguide switch apparatuscomprising: a straight rectangularwaveguide section of substantially uniform internal cross sectionthroughout its length; a substantially at rectangular metallic shuttervane having a thickness which is a minor fraction o f any internallcross-sectional dimension of said waveguide section, said .vane beingdimensioned in the length and width directions perpendicular to itsthickness dimension elfectively -to lill the internal cross sectionofsaid waveguide Vwithout touch-V an axis of symmetry of -the guidesectionl and the vane,

to each of two ixed positions, one of'which is aclosed positiontransversely of the guide section and the other of which is an openposition parallel to the guide section axis; and metallic bodies ofsubstantially cylindrical cross section, each having a diameter which isof the order of half the dimension of said vane in said widthldimension, permanently affixed to each narrow side edge of said vaneconcentric with the rotational axis thereof, eachof said bodiespresenting a substantially circular surface adjacent and spaced from theconfronting narrow Wall por-v tions, respectively, of the waveguidesection, said bodies being dimensioned Aand located to constituteaxially sym# metrical lumped inductance elements for matching thecapacitive reactance -across the waveguide section introduced by thevane in the openposition. I

3. Waveguide switch apparatus comprising: a straight rectangular"waveguide section of substantially uniform internal cross vsectionthroughout its length;,a substantially hat rectangular metallic shutterVane having a thickness which isa minor ifraction of any internal:crosssectional dimension of said waveguide section, saidvane beingdimensioned in the-length and width directions perpendicular to itsthickness dimension elfectively to ll the internal `transversecross-section of said waveguide without touching any ofthe wallsthereofymeans for mounting the shutter Ivane for rotation within saidguide section, about an axis of symmetry of the guide section and thevane, to each of two fixed positions, one of which is a closed Vpositiontransverselyot the guide section -and thev other of whichis anopen-position parallel ,to the guide section axis; metallicbodies ofsubstantially `cylindrical cross section permanently aixed to eachnarrow side edgeofsaid yaneconcentric with the-rotational axis thereof,each of said bodies presenting .e ,substantially circular surfaceadjacent and spaced from the con- -fronting narrow wallportions,'respectivelof the wave-V guide section, said bodies-beingdimeusioned and klQCited to constitute axially symmetrical lumpedinduetanceelermeritsy for matching the capacitive reactance l across thewaveguide section introduced by the vane vin the open pastion;ythelength--of-.said wavesuidesection being only slightlygreaterthan lthedimensione; said vane in said width direction, said `waveguide sectionbeing -itted at each' ,6nd, lWith tranSveIsely Yontwardly extending angemeans forzattachingrsaid waveguide section insaO waveguide transmissionline; 'andsactuatingf means contained substantially entirelywithinvtheannular space outside said waveguide section bounded by vsaid;ange :means for rotating said vane between .each .o f said twoxedpositions. e i,

4. Waveguide switch apparatus according to Vclaim .3 in whichtheactuatingrmeans', comprises a lshaft extending from the -vanelthroughthe waveguide section; ,magnet core means arranged aroundtheperipheryofsaid .waveguide `section` and having an .airqgap therein;coil means on said core means adapted to establishamagnetic eld in saidcore means; permanent magnet armaturemeans aixed to said shaftwithinsaid ,air:gap; and .biasing means connected between said waveguide.sectiontandsaid shaft urging the vane torotate in lone directionv.Opposed to the direction in which said-.armature means liis .urged vbysaid magneticeld when said-.core meansisgenergized; whereby thevane canbe rotated betweensaid two positions by establishing andgremoving theeld.

5. Vwaveguide switch -apparatus comprising: astraight rectangularywaveguide section `of substantially `uniform internal vcross section.thronghout itsalengthya substantially Ailat Irectangularmetallieshutter .vaneghaving substantially flat edgesand-,agthicleuessiwhich isaminor fraction `of any internalcrossesectional dimension Aof said waveguide section, said ,vane :beingdimensioned-.in the length'and width directionsperpendicular.toits-,thickness dimension Aeffectively to ,lill the vinternal transverse cross section of 'said .waveguide withouttouchingany of the 1 walls, thereof; means for vmounting:theshutter.vaneforrotation within fsaidguide section, `about :an ,of symmerry` ofthe guidesection and the fvane/,vtoeach of two xed positions, one .ofwhichtisacl'osedpositiontransversely-of the guide Vrsection f andtheother offwhich is .an open position parallel :lo the guide sectionaxis; vmetallic bodies of Asubstantially cylindrical cross sectionApermanently axed to Yeach narrowside edge .ofjsaid vane concentric with,1t-he rotational ,axis thereof, -each of said bodiesfpresentingasubstantially ,circular surface adjacent and spaced -from .the Lconfronting narrow .wall portions, respectively, of thewaveguide-section, said bodies -being dimensioned Vand located to:CQnStituIeiaXially asymmetrical lumped inductance elements for matchingthe capacitive reactance .-across the waveguide isecton :introduced `bythe vane intheopen position; andren iris opening in said vane,resonan t.at 'afirequency `vwhieh'is high relative to the intendedoperatingfrequeneyof ,the Awaveguide, said in's inductance gbeing z.resonantsubstantially at said operating frequeney with theoapacitance existingbetween ,the c-at edges :of `the .shutter vane and ,the adj acent widewalls of. said waveguide section when the vane is in Isaid closedposition, -wl1erebvssaid vane nsaid closed position providesasubstantially complete short circuit across said waveguide section at'4s-aid operating frequency. y

. References Cited y inthe'iile ofy this patent 'UNITED -STATES 'PATENTS2,175,046 Warner v O ct. 3, 1939 2,480,189 I-rving,.. Ang. 30, 19492,573,713 Kannenbergy Nov. '6, 1 951 2,814,782 z neski `Nov. 26, 19572,816,272 Braden Dec. 10, 1957

